1. Field of the Invention
The present invention relates to optical fiber ferrule structures, in particular a hermetic optical fiber alignment assembly including a ferrule for aligning optical fibers.
2. Description of Related Art
Given the increasing bandwidth requirements for modern day data transmission (e.g., for high definition video data), fiber optic signal transmissions have become ubiquitous for communicating data. Optical signals are transmitted over optical fibers, through a network of optical fibers and associated connectors and switches. The optical fibers demonstrate a significantly higher bandwidth data transmission capacity and lower signal losses compared to copper wires for a given physical size/space.
In fiber optic signal transmission, conversions between optical signals and electrical signals take place beyond the terminating end of the optical fiber. Specifically, at the output end of an optical fiber, light from the optical fiber is detected by a transducing receiver and converted into an electrical signal for further data processing downstream (i.e., optical-to-electrical conversion). At the input end of the optical fiber, electrical signals are converted into light to be input into the optical fiber by a transducing transmitter (i.e., electrical-to-optical conversion).
The opto-electronic devices (receiver and transmitter and associated optical elements and electronic hardware) are contained in an opto-electronic module or package. The optical fiber is introduced from outside the housing of the opto-electronic module, through an opening provided in the housing wall. The end of the optical fiber is optically coupled to the opto-electronic devices held within the housing. A feedthrough element supports the portion of the optical fiber through the wall opening. For a variety of applications, it is desirable to hermetically seal the opto-electronic devices within the housing of the opto-electronic module, to protect the components from corrosive media, moisture and the like. Since the package of the opto-electronic module must be hermetically sealed as whole, the feedthrough element must be hermetically sealed, so that the electro-optic components within the opto-electronic module housing are reliably and continuously protected from the environment.
Heretofore, hermetic feedthrough is in the form of a cylindrical sleeve defining a large clearance through which a section of the optical fiber passes. The optical fiber extends beyond the sleeve into the opto-electronic module. The end of the optical fiber is terminated in a ferrule (separate from the sleeve) that is aligned with the opto-electronic devices provided therein. A sealing material such as epoxy is applied to seal the clearance space between the optical fiber and inside wall of the sleeve. The sleeve is inserted into the opening in the opto-electronic module housing, and the opening is sealed, typically by soldering the exterior wall of the sleeve to the housing. The outside wall of the sleeve may be gold plated to facilitate soldering and improve corrosion resistance.
Given the large clearance between the sleeve and the optical fiber and the use of epoxy to seal such clearance (i.e., a layer of epoxy between the external fiber wall and the inside wall of the sleeve), the sleeve does not support the optical fiber with any positional alignment with respect to the sleeve. Given the sealing material provides stress and strain relief for the section of optical fiber held therein, the brittle fiber does not easily break during handling. The sleeve essentially functions as a grommet or conduit that is sealed to the opto-electronic module housing and that allows the optical fiber to pass through in a hermetic seal within the sleeve. As noted below, the end of the optical fiber needs to be aligned to the opto-electronic devices to within acceptable tolerances by means of a ferrule.
To optically couple the input/output of the optical fiber to the opto-electronic devices in the opto-electronic module, optical elements such as lenses and mirrors are required to collimate and/or focus light from a light source (e.g., a laser) into the input end of the optical fiber, and to collimate and/or focus light from the output end of the optical fiber to the receiver. To achieve acceptable signal levels, the end of the optical fiber must be precisely aligned at high tolerance to the transmitters and receivers, so the optical fiber are precisely aligned to the optical elements supported with respect to the transmitters and receivers. In the past, given the internal optical elements and structures needed to achieve the required optical alignments at acceptable tolerance, coupling structures including a connection port is provided within the hermetically sealed opto-electronic module housing to which a ferrule terminating the end of the optical fiber is coupled. The transmitters and receivers and associated optical elements and connection structures are therefore generally bulky, which take up significant space, thereby making them not suitable for use in smaller electronic devices. Heretofore, opto-electronic modules containing transmitters and receivers are generally quite expensive and comparatively large in size for a given port count. Given optical fibers are brittle, and must be handled with care during and after physical connection to the coupling structure within the opto-electronic module and to avoid breakage at the feedthrough sleeve. In the event of breakage of the optical fiber, it has been the industry practice to replace the entire opto-electronic module to which the hermetic optical fiber feedthrough is soldered. The connection and optical alignment of the optical fibers with respect to the transmitters and receivers must be assembled and the components must be fabricated with sub-micron precision, and should be able to be economical produced in a fully automated, high-speed process.
The above noted drawbacks of existing fiber optic data transmission are exacerbated in multi-channel fiber transmission.
OZ Optics Ltd produces multi-fiber hermetically sealable patchcord with glass solder having multiple optical fibers passing through a sleeve, with the optical fibers extending beyond the sleeve, with the ends of the optical fibers held in an alignment ferrule separate from the sleeve. OZ Optics Ltd further produces a multi-fiber hermetically sealable patchcord with metal solder, in which the optical fibers are coated with a metal (metalized fibers). The optical fibers are terminated with a silicon ferrule that is supported within a sleeve, which is a component separate from the ferrule. The outside wall of the sleeve is gold plated for sealing to an opto-electronic module housing. However, these multi-fiber hermetic feedthrough configurations do not appear to resolve the drawbacks of the prior art noted above, and introduce additional complexity and cost at least from a manufacturability perspective.
What is needed is an improved hermetic optical fiber alignment assembly, which improves optical alignment, manufacturability, ease of use, functionality and reliability at reduced costs.